Such prior application discloses a horizontal barometric leg of the type shown in Pagan U.S. Pat. No. 4,783,291. In the Pagan patent, a vacuum chamber includes an extrusion die at one end forming an extrudate. After passing through sizing, calibration and draw off equipment, for example, the extrudate exits the vacuum chamber through a water baffle. The extrudate passes over a dam and dips into a pond to exit the chamber through the pond. The pond has two sections or levels, one with a higher level within the chamber during vacuum and one with a lower level outside the chamber. A circulating system keeps the pond level within the chamber from overtopping the dam during vacuum extrusion. The pond provides full immersion cooling during vacuum extrusion as well as providing a continuous water baffle seal for the extrudate exiting the chamber. The extrudate may be cut and processed in atmosphere after it leaves the lower level or section of the pond outside the chamber.
In such prior Lightle, et al. application there is disclosed a horizontal barometric leg vacuum extrusion line with a support truss extending from the dam to a fixed bulkhead, the die being mounted on the end of the extruder projecting through the fixed bulkhead. Calibration and sizing or draw-off equipment is mounted on the truss.
The chamber surrounding the truss includes a fixed section and a telescoping section which can move away from the bulkhead telescoping over the fixed section to provide access to the die and the downstream equipment.
If some of the downstream equipment is within the fixed section, the fixed section is entered as one would a cave or tunnel. The system with the single movable section telescoping over the fixed section is quite adequate for medium to low through-puts, but is not necessarily adequate for large through-puts and/or extrudate cross-sections with foaming extrudates. Through-puts are normally expressed as pounds or kilograms per hour. For example, smaller through-puts typically may be two hundred pounds per hour or less, while larger through-puts may typically be two thousand pounds per hour or more.
When a mishap or mayhap occurs, especially during system start-up, the operators need to open the chamber quickly and obtain access to the errant downstream equipment quickly. The operators not only need access quickly, they need access with an adequate spatial working environment. Without such, the vacuum chamber may literally fill up or start to fill up with extrudate, especially foam extrudate, requiring the whole system to be shut down.
With higher through-puts, problems need to be addressed more quickly, and the chamber of the system requires larger volume around the downstream equipment, not only to accommodate the equipment, but also operators around the equipment with adequate spatial working environment to obtain access to the equipment and any misdirected extrudate.
The vacuum chamber of the present invention utilizes a fixed large diameter entrance bulkhead plate. A first section with a large diameter is movable and seals against a second larger section, and telescopes over a smaller diameter fixed section which includes the dam and the higher level portion of the pond of the water baffle seal. The second larger section may move within the gap created by movement of the first, and seals against the first and entrance bulkhead plate. A truss supporting the downstream equipment extends from the dam to the fixed bulkhead through the movable large diameter sections. In this manner all of the downstream equipment may be mounted within the two movable large diameter sections providing adequate volume for large through-puts as well as a good spatial working environment.
Both large diameter sections may quickly be opened with the first telescoping over the smaller fixed section, and the second section may be moved with the first section or within the gap provided by the first section. In this manner any portion of the downstream equipment may quickly be completely exposed.
The first section may be locked to the fixed section, and fluid seals may be employed between the bulkhead and second section, the first and second section, and the first section and fixed section, quickly to reestablish the integrity of the vacuum chamber. Both larger diameter sections may be power operated to move concurrently or independently.
In order to achieve quick access and to open and lock the vacuum chamber, there is provided a simplified quick acting preferred lock system between the fixed and a moving section of the vacuum chamber. The lock system utilizes pneumatic piston-cylinder assemblies driving lock blocks behind fixed stop blocks, forcing the sections together in a direction opposite the forces generated by the fluid seals. The preferred lock system may be utilized whether the fixed and moving sections are substantially the same size or substantially different in size.
To the accomplishment of the foregoing and related ends, the invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.